Exhaust tip shield



y 7, 1959 s. G. CRESSWELL 2,893,027

EXHAUST TIP SHIELD Filed Sept. 12, 1958 INVENTOR 'ieyvfiezz i'fesszrel ATTORNEY United States Patent EXHAUST TIP SHIELD Stephen G. Cresswell, Mill Hall, Pa., assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Application September 12, 1958, Serial No. 760,657

3 Claims. (Cl. 15-21) The invention relates to an improvement in a pin bufling machine such as is utilized in the process of manufacturing an electron tube.

In some types of electronic tubes, the stem portion embodies a circular array of contact pins surrounding a sealed off glass tip, which pins must be buffed in order to put them in better condition for soldering. Usually this is done immediately after the tube has been tipped off. That is to say, this is done immediately after an evacuated glass bulb with integral glass suction tubulation has been sealed off by fusing the glass tubulation adjacent the bulb, leaving a glass tip and while the glass tip is still hot. The buffing operation on the pins is performed by motor driven brushes and these brushes in the past created air turbulences about the still hot glass tips resulting in unequal cooling of the glass bulb and tip and cracking of the tip, with consequent shrinkage of output.

It is an object of this invention to provide, in the buffing machine, a means to eliminate the glass tip cracking due to the air disturbances created by the bufling brushes.

Other objects will be apparent after considering the following specification when taken in conjunction with the accompanying drawings in which:

Fig. 1 is a plan view of the portion of the buifing machine incorporating the invention.

Fig. 2 is an elevational view of the structure shown in Fig. 1. s

Fig. 3 is a section taken on the line 3-3 of Fig. 1, looking in the direction of the arrows, and

Fig. 4 is a view of the air shielding cup forming part of the invention.

Referring to the drawings in greater detail, at 10, Figure 1, is a standard having secured thereto, as by screws 12, a retainer 14 for a lower stripper plate 16 held in a recess in the lower face of the retainer 14 by a spring -C-ring 18. The upper face of the lower stripper plate is flush with the upper surface of the retainer. Also upstanding from the stripper plate 16 is a guide pin 17. The stripper plate 16 is provided with a circular array of equally spaced upwardly diverging holes 20. It is further provided with a central bore 22 within which is force fit or otherwise positioned a metallic cup 24 with flaring mouth 26 and if desired, in its bottom, a small dust releasing hole 28. The upper edge of the cup extends upwardly no farther than the upper surface of plate 16 and extends well down below it to freely accommodate the hot sealed off glass tip 30 of the electron tube 32 whose pins 34 are to be buffed, as when they are buffed preliminarily to their being solder-connected to the contacts of a phenolic base. When the pins of the tube are in place to have them buffed, they extend below the plate 16 and extend to or beyond the lower face of the retainer 14.

Mounted on a fixed support is a motor 36 whose shaft 38 is threaded and extends diametrically across and in a plane below the cup 24. Mounted on the shaft is a pair of rotary cylindrical brushes 40, the hubs 42 of which are held in spaced relationship on the motor shaft by lock nuts 44. The brushes are in position so that when driven they will engage two or more pins on the electron tube, in this stage of operation. In other and subsequent stages, a second motor with a second pair of brushes will be arranged to engage others of the pins. These brushes when rotating, unfortunately, cause air drafts which ex cept for the cup 24 would very often cause cracks to appear in the tube tip 30.

To facilitate removal of the pin buffed tube from the lower plate 16, an upper centrally recessed stripper plate 46 is provided, this plate being provided with upwardly flaring holes 48 registering with the holes 20 in the lower plate and guided for vertical movement along the guide pin 17, the guide pin serving to initially position the electron tube pin receiving holes in the two plates in registration. A central downwardly tapering opening 50 is provided in the upper plate to guide the tip of the bulb into the cup below. The stripper plate 46 is held to a vertically reciprocatable retainer plate 52 by arcuate clamp bars 54 and screws 56 threaded into the retainer plate 52. Suitable means such as post 58, is provided to lift the upper stripper plate and tube away from the lower plate 16, for ease in removal of the tube from the bufling machine. The post may be vertically reciprocated in any convenient fashion as by a cam engaging the lower end of the post, not shown.

When a tube just exhausted and tipped off has been seated in the upper stripper plate and the post has been lowered, the hot tip lies protected within the cup 24 while the brushes play against the pins of the electron tube, these pins being external of the cup. Therefore, there is no possibility of cracking of the tip due to air disturbances created by the brushes or for other reasons, with a marked reduction of shrinkage of tubes due to tip cracking.

The hole 28 in the bottom of the cup allows fine debris to fall out therefrom, but is not essential.

Having thus described the invention, what is claimed is:

1. A pin bufiing machine comprising a plate having openings for receiving the pins of an electron tube, with said pins adapted to extend below the plate and near the center of the plate, a pin cleaning device whose movement creates air disturbances and means to drive the same, with the device operating against at least one extending pin of the tube to clean the same, a shield means mounted centrally in said plate, said shield means being substantially air impervious in the region below the plate.

2. A pin buifing machine comprising a plate having a circular array of openings for receiving the pins of an electron tube, a central opening in said plate, a cup seated in said central opening of the plate, and motor driven brushes external of the cup and operative on pins of the electron tube inserted through the plate to clean the pins.

3. A pin buifing machine comprising a plate having a circular array of openings therethrough and a central opening, a cup seated within said central opening, a stripper plate above the first plate having openings registering with the central opening and circular array of openings in the first plate, means for raising and lowering the stripper plate, rotary cylindrical brushes positioned adjacent and below openings of the circular array of openings of the plate, and external of the cup, and means for driving said brushes.

No references cited. 

